The present invention generally relates to an implantable cardiac lead for use with an implantable cardiac stimulation device. The present invention more particularly relates to such a lead and method of making the same wherein the lead includes strain relief to protect the lead connector from damage when the lead connector is withdrawn from an associated device.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are positioned within the heart for making electrical contact with desired heart chambers. Conductors within the leads couple the electrodes to a connector of the lead which in turn is received by a mating connector within a connector receiving cavity of the device. This then couples the electrodes of the lead to the device to enable the device to sense cardiac electrical activity and deliver the desired electrical therapy with the electrodes.
The connection system described above also provides for the leads to be disconnected from the device at a later time to allow for device replacement, usually due to battery depletion of the generator. This requires the implanted lead connector to be able to be disconnected from the device without the connector becoming damaged. This is critical since implanted leads are nearly always left in place and intended to be re-used with the new, replacement device.
Implantable leads and their lead connectors are typically designed to be very flexible and are assembled using adhesive bonds, crimps and welds that form joints in the lead connector. As a result, the lead connector joints and materials are able to withstand only very limited applied disconnection and lead connector withdrawal forces. However, the lead connector joints and the lead connector materials are often exposed to much greater forces during the disconnection. Much higher removal forces are often required because of swelling in the materials on the lead connector interface with the device connector cavity securing mechanisms after several years of implant. This can cause the lead connector to stick inside the cavity. Thus, the much higher withdrawal forces are often necessary to remove the lead connector from the device connector cavity. Such forces can severely damage the lead connector and then render the lead connector to be dysfunctional. Moreover, it can be very difficult or even impossible for the physician to be able to discern whether the lead connector has been damaged. Thus, a damaged lead connector can often become re-used with a new device without it being known that the connector is damaged. This can result in significant clinical problems.
The present invention overcomes the problems and disadvantages of prior art lead connectors by providing strain relief within a lead connector to protect the lead connector from damage during its disconnection from an associated device.
In accordance with the broader aspects of the present invention, the strain relief is provided by a strain relief member which is connected between a connector terminal and a conductor of the lead that couples a lead electrode to the connector terminal.
In accordance with the present invention, the lead is elongated and has a distal end, a proximal end, an electrode, and a conductor coupled to the electrode and extending to the proximal end of the lead. A connector on the lead proximal end connects the conductor to a mating implantable device connector. The lead connector includes a terminal coupled to the conductor and a string relief member connected between the conductor and the terminal.
In accordance with a particular aspect of the present invention, the connector further includes an anchor longitudinally fixed on the lead proximal to the terminal. The strain relief member is connected between the anchor and the connector terminal.
The lead connector includes a body and the anchor is preferably affixed on the lead conductor within the connector body.
The strain relief member is preferably formed of a flexible, non-stretchable material, such as a flexible, non-stretchable cable fabricated with a suitable metal alloy material. The strain relief member may more preferably be formed of a nickel metal alloy, such as MP-35N.
The connector terminal preferably includes a pin terminal having a crimp sleeve secured to the conductor. The relief member then preferably extends between the anchor and the crimp sleeve.
The present invention still further provides a method of providing an implantable cardiac lead with a connector having strain relief wherein the lead is elongated and has a distal end, a proximal end, an electrode at the distal end, and a conductor coupled to the electrode and extending to the proximal end. The method includes the steps of securing a connector body to the proximal end of the lead, providing the connector body with a terminal, affixing an anchor within the lead body distal to the terminal, coupling the terminal to the lead conductor, and connecting a strain relief member between the anchor and the terminal.